Sea Watch, a German charity, said it had been alerted to the disaster by Italy's coastguard, which believed 150 people had been aboard.

Al Jazeera's Mahmoud Abdel Wahed, reporting from the Libyan capital, Tripoli, said the boat had set sail from the eastern town of Garbouli.

"Libya's coast guard says it had no role in the rescue operation and that it was taken care of by Italy's coast guard," he said. "The boat was small and in a bad condition – it capsized in international waters. The Libyan coast guard said they cannot spot these boats because they are usually small, unless there is a distress call."

The International Organization for Migration describes the Mediterranean Sea as the world's deadliest border. Last year, 3,116 people died trying to cross from North Africa to Europe, it said.

More than 119,000 refugees and asylum seekers arrived in Italy by sea last year, it said. The figure is roughly one-third drop over the previous year.